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WWF works to sustain the natural world for the benefit of people and wildlife, collaborating with partners from local to global levels in nearly 100 countries.
Thundering herds of buffalo kicking up clouds of dust. Flocks of birds so thick they create shadows on the ground. These images come to mind when speaking about wildlife spectacles or animal migrations. These amazing sights happen, not only in the air and on land, but also underwater in rivers around the world. Perhaps the most extraordinary migration is the nearly 3,728-mile trip gilded catfish (B rousseauxii) make between the lower Brazilian Amazon to their spawning grounds in the Andean piedmont of Bolivia, Colombia, Ecuador, and Peru. In the Mekong Basin alone, there are an estimated 1,000 fish species and 87% of fish species with known life histories are migratory[i]. However, the migrations of all these species are under increasing threat. And, as we lose these river corridors, we lose the benefits that connected rivers provide to humans too—in terms of food from fisheries and floodplain agriculture, water supply from recharged groundwater sources, delivery of sediments and nutrients to downstream floodplains and deltas, and the many recreational, cultural, and spiritual values that connected rivers provide.
We know human activities are interrupting air and land migrations, but people have also created obstacles that block or affect freshwater species migrations, as well as the flows of sediments, nutrients, and water within rivers around the world. On the Madeira River in Bolivia, fish catchii declined by 39% after construction of dams affecting a main source of livelihood and protein for local communitiesiii.
The good news is that we have solutions to maintain or restore river connectivityiv. We simply need these tactics to be more widely adopted by leaders and practitioners when making planning and management decisions for water resources and in the design and construction of infrastructure that impacts them.
Strategic decisions early in water resources and energy development can avoid placement of infrastructure in locations most degrading to ecosystems and the services they provide. Early planning also supports consideration of alternative development options for new infrastructure which could be less impactful. In Zambia, the government is developing a long-term strategy to meet the nation’s projected energy demands in a sustainable, reliable and affordable way, including consideration of additional capacity from energy technologies such as solar and wind and alternative storage optionsv. These options will make it more likely that Zambia can provide low cost and low carbon power for its people and economy while minimizing additional damming of free-flowing rivers.
Another aspect of avoidance is putting in place protections for important river corridors to ensure maintenance of connectivity over the long term. The Albanian government has recently taken steps to protect the Vjosa River, rare in Europe due to how it retains its natural flow dynamics, including sediment flows and floodplains. Work is already underway to upgrade the protection level of the Vjosa River Basin and its free-flowing tributaries to an IUCN Category II Level National Park with the river corridor itself to be protectedvi.
Where new infrastructure such as culverts, levees, and dams is deemed necessary, siting, structure design and operation will be critically important for minimizing impacts. For example, the addition of a passage facility at the site of the Pak Peung wetland along the Mekong River in Laos, where irrigation infrastructure has been blocking the movement of species into the wetland, allowed passage of 100 fish species and fish catch became greater in the late wet season as compared to a no-fish pass control sitevii.
Reconnecting freshwater systems that have already been fragmented can lead to quick improvements to the health of and benefits from aquatic ecosystems. In locations where infrastructure has been removed and species are still present, recovery can be dramatic. One such example comes from the River Villestrup in Denmark. Six weirs were removed and the brown trout smolt run went from 1,600 to about 19,000 from 2004 to 2015 and the spawning population from 350 to 3,600viii. Thus, restoration is critically important to bending the biodiversity curve where fragmentation has hammered freshwater species populations.
Restoring floodplains and recharging groundwater sources are also critical for flood control and water supply, especially in an era of increasing floods and water scarcity. In Thailand, the Ing River floodplain stores and conveys floodwaters and was credited with sparing a neighboring village from inundation during a major flood in 2010ix.
We have the tools to act now. First, avoiding barriers in the most harmful locations and/or via protections for critically important freshwater connectivity corridors. Second, mitigating impacts where barriers are inevitable via barrier design or dam re-operation for environmental flows. And third, restoring rivers, floodplains, and the recharge of groundwater.
With the recent launch of the country-led Freshwater Challenge aiming to restore and conserve 865 million acres of wetlands and 186,411 miles of rivers globally and with the explicit inclusion of “inland waters” in the targets of the new global biodiversity agreementx, the moment is now to take these steps. We are risking further degradation of our rivers and the life they support, including the majestic species migrations that drive our imagination. Our imagination should know no bounds, neither should our ambition or our commitment to act.
[i] Baran, E. Fish Migration Triggers in the Lower Mekong Basin and Other Freshwater Tropical Systems; MRC Technical Paper No.14; Mekong River Commission: Phnom Penh, Cambodia, 2006
ii Mean annual fish catch.
iiiSantos, RE, Pinto-Coelho, RM, Fonseca, R, Simões, NR, Zanchi, FB. The decline of fisheries on the Madeira River, Brazil: The high cost of hydroelectric dams in the Amazon Basin. Fish Manag Ecol. 2018; 25 : 380-391. https://doi.org/10.1111/fme.12305
ivThieme, M., Birnie-Gauvin, K, Opperman, J.J., Franklin, P.A., Richter, H., Baumgartner, L., Ning, N., Vu, A.V., Brink, K., Sakala, M., O’Brien, G.C., Petersen, R., Tongchai, P. and Cooke, S.J. 2023. Measures to Safeguard and Restore River Connectivity. Journal: Environmental Reviews. https://doi.org/10.1139/er-2023-0019.
vThieme, M., Birnie-Gauvin, K, Opperman, J.J., Franklin, P.A., Richter, H., Baumgartner, L., Ning, N., Vu, A.V., Brink, K., Sakala, M., O’Brien, G.C., Petersen, R., Tongchai, P. and Cooke, S.J. 2023. Measures to Safeguard and Restore River Connectivity. Journal: Environmental Reviews. https://doi.org/10.1139/er-2023-0019.
viiBaumgartner, L.J., Collier, P., Conallin J, Ning, N., Robinson, W.A., Cooper, B., Crase, L., Homsombath, K., Singhanvouvong, D., Phonekhampheng, O., Thorncraft, G., and Marsden, T. 2022. Quantifying biophysical and community impacts of improved fish passage in Lao PDR and Myanmar - Final Report. ACIAR Report Series, FR2022-021. ISBN: 978-1-922787-29-3.
viiiBirnie-Gauvin, K., Candee, M.M., Baktoft, H., Larsen, M.H., Koed, A., and Aaerestrup, K. 2018. River connectivity reestablished: Effects and implications of six weird removals on brown trout smolt migration. River Research and Applications 34(6): 548-554.
ixThieme, M., Birnie-Gauvin, K, Opperman, J.J., Franklin, P.A., Richter, H., Baumgartner, L., Ning, N., Vu, A.V., Brink, K., Sakala, M., O’Brien, G.C., Petersen, R., Tongchai, P. and Cooke, S.J. 2023. Measures to Safeguard and Restore River Connectivity. Journal: Environmental Reviews. https://doi.org/10.1139/er-2023-0019.